Molecular Dynamics Study Of Different Water States In The Poly (Vinyl Alcohol) Chemical Hydrogel

Hydrogel is one of the most important function materials.It can be use in the manufacture of artificial organism including artificial cartilage,artificial cornea,to replace damaged tissue.Some hydrogel can be applied in the sensor field because of its sensitive response to physical and chemical stimuli from external environment.Hydrogel has widespread application in many fields due to its excellent mechanical,physical and chemical properties.Therefore,it makes great sense to study the mechanical constitutive relations of hydrogel.Up to now,the effect of different water state in hydrogel on its mechanical properties hasn't been researched clearly in most of the existing works.In the deformation of Polymer physical hydrogels,the number,position and strength of crosslinking points can be changed,which makes the existing constitutive relations of hydrogel inappropriate to use.So it is important to distinguish different water states and its content in hydrogel.Poly(vinyl alcohol)chemical hydrogel was used in this paper.Hierachy affiliation and stratification rule of water was proposed based on the connectivity condition in the olymer chemical hydrogels.Molecular dynamics simulation was used to calculate the content of water in different states in poly(vinyl alcohol)chemical hydrogel.The results were compared to our DSC experiments.The characteristic peaks in hydrogels with different contents of water were confirmed according to the experimental results from Raman spectroscopy test.After the comparison of the result obtained from molecular dynamics simulation DSC and the Raman spectroscopy test,it can be concluded that the first,second,and third layer water was respectively non-freezing water and freezing water.The other layers water were free water.Hierachy affiliation and stratification rule of water proposed in this paper can clearly described the microstate of different water states.